Seminar"From Basin-Scale Currents to Coastal Fronts in the Bay of Bengal: Understanding Transport Through Lagrangian Coherent Structures" by Prof. Sourav Sil

[Speaker]

Prof. Sourav Sil
School of Earth, Ocean and Climate Sciences
Indian Institute of Technology Bhubaneswar, India

[Abstract]

The Bay of Bengal (BoB) exhibits complex ocean circulation driven by monsoon winds, freshwater input, coastal currents, and mesoscale eddies. Understanding how these processes transport heat, nutrients, sediments, and pollutants require identifying the pathways and boundaries that organize water movement across scales. Lagrangian Coherent Structures (LCSs) are dynamically defined material lines in fluid flows that attract, repel, or guide passive tracers, thereby organizing their transport and mixing.

This talk explores LCSs across basin, mesoscale, and coastal scales using satellite-derived surface currents and high-resolution numerical simulations. At the basin scale, Finite-Time Lyapunov Exponents (FTLE) identify parabolic and hyperbolic structures associated with the Western Boundary Current (WBC), East India Coastal Current (EICC), and Coastally Trapped Kelvin Waves (CTKWs). These structures reveal seasonal transport barriers, convergence zones, and pathways controlling coastal–offshore exchange. At the mesoscale, Lagrangian-Averaged Vorticity Deviation (LAVD) -based analysis reveals three-dimensional coherent eddy cores and simultaneous upward and downward transport within cyclonic and anticyclonic eddy cores. At the coastal scale, newly classified coastally attached LCSs explain persistent fronts, sharp tracer gradients, and contrasting patterns of coastal water retention and offshore exchange.

These findings demonstrate how LCSs can improve understanding of freshwater plume dispersal, marine ecosystem dynamics, and coastal pollution transport, with applications in environmental monitoring and ocean forecasting.